From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id A03BC396D23 for ; Sat, 25 Apr 2026 12:55:47 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.129.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777121749; cv=none; b=N7oAG1GEVn9TfYvSc85VtRvmJ+IWse4sRJB3ae25Y5VFBv43dT07J9w7fp/BoMzYjrJbRnei8YMFp8f/Y6e0eYbYrjW+mxTR29zxLhZCHJsnfnMAmFKSHKZX6hyqiLIZv5Dd9ZGwyJ+Veg0A9fTcIF+ewnjKjicKvEWXqt4nOlE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777121749; c=relaxed/simple; bh=DRDJmYHK2ygS9wWeSeTfVKgUxwyN0xYD1MJVVOt5lpk=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=WDOXlDyXwcyQ77XFrkfbAmwV+zIod+/O/enH1gi3ys71/ZbnIScKchVJKUeR8+a2oETPGOvDnGNghIR4DENAg7Fodj8WwdBmQs/wMrY9Lwthb+coAtLuQjFIkEbHzqScsktRU7WVEiviWjsDwO99Pzm1fYicVpvh1ZbH9UtfEkM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=hywpfKsW; arc=none smtp.client-ip=170.10.129.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="hywpfKsW" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1777121746; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=9+HCNdbgI96Ai70MhVVTZqmH4nl/dl7bHmAA/USf8Fc=; b=hywpfKsWIwVZcLXSW9tft2IBl6cU97mncTG1gSOwgBMSykwWHy0aQEb2RlET1PHInC9ajE YnMLxj4yEvA8287UML4bAN1wfxcZttoWCfbAznX367nEFnAyiPOKnW50J+fraQaYAPwBH8 MBWAIZCQ7hF7ZwzCwpmbOzTmROXknQk= Received: from mx-prod-mc-05.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-503-6NAkiPYJNwigtP-mOOAp-A-1; Sat, 25 Apr 2026 08:55:43 -0400 X-MC-Unique: 6NAkiPYJNwigtP-mOOAp-A-1 X-Mimecast-MFC-AGG-ID: 6NAkiPYJNwigtP-mOOAp-A_1777121742 Received: from mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.111]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-05.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 301DF195609F; Sat, 25 Apr 2026 12:55:42 +0000 (UTC) Received: from warthog.procyon.org.com (unknown [10.44.48.17]) by mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 3F52E1800351; Sat, 25 Apr 2026 12:55:39 +0000 (UTC) From: David Howells To: Christian Brauner Cc: David Howells , Paulo Alcantara , netfs@lists.linux.dev, linux-afs@lists.infradead.org, linux-cifs@vger.kernel.org, ceph-devel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, Matthew Wilcox Subject: [PATCH v3 14/19] netfs: Fix folio->private handling in netfs_perform_write() Date: Sat, 25 Apr 2026 13:54:18 +0100 Message-ID: <20260425125426.3855807-15-dhowells@redhat.com> In-Reply-To: <20260425125426.3855807-1-dhowells@redhat.com> References: <20260425125426.3855807-1-dhowells@redhat.com> Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.111 Under some circumstances, netfs_perform_write() doesn't correctly manipulate folio->private between NULL, NETFS_FOLIO_COPY_TO_CACHE, pointing to a group and pointing to a netfs_folio struct, leading to potential multiple attachments of private data with associated folio ref leaks and also leaks of netfs_folio structs or netfs_group refs. Fix this by consolidating the place at which a folio is marked uptodate in one place and having that look at what's attached to folio->private and decide how to clean it up and then set the new group. Also, the content shouldn't be flushed if group is NULL, even if a group is specified in the netfs_group parameter, as that would be the case for a new folio. A filesystem should always specify netfs_group or never specify netfs_group. The Sashiko auto-review tool noted that it was theoretically possible that the fpos >= ctx->zero_point section might leak if it modified a streaming write folio. This is unlikely, but with a network filesystem, third party changes can happen. It also pointed out that __netfs_set_group() would leak if called multiple times on the same folio from the "whole folio modify section". Fixes: 8f52de0077ba ("netfs: Reduce number of conditional branches in netfs_perform_write()") Closes: https://sashiko.dev/#/patchset/20260414082004.3756080-1-dhowells%40redhat.com Signed-off-by: David Howells cc: Paulo Alcantara cc: Matthew Wilcox cc: netfs@lists.linux.dev cc: linux-fsdevel@vger.kernel.org --- fs/netfs/buffered_write.c | 77 +++++++++++++++++++++--------------- include/trace/events/netfs.h | 2 + 2 files changed, 48 insertions(+), 31 deletions(-) diff --git a/fs/netfs/buffered_write.c b/fs/netfs/buffered_write.c index c7b49b38a710..0439a4c2e003 100644 --- a/fs/netfs/buffered_write.c +++ b/fs/netfs/buffered_write.c @@ -12,12 +12,6 @@ #include #include "internal.h" -static void __netfs_set_group(struct folio *folio, struct netfs_group *netfs_group) -{ - if (netfs_group) - folio_attach_private(folio, netfs_get_group(netfs_group)); -} - static void netfs_set_group(struct folio *folio, struct netfs_group *netfs_group) { void *priv = folio_get_private(folio); @@ -157,6 +151,7 @@ ssize_t netfs_perform_write(struct kiocb *iocb, struct iov_iter *iter, size_t offset; /* Offset into pagecache folio */ size_t part; /* Bytes to write to folio */ size_t copied; /* Bytes copied from user */ + void *priv; offset = pos & (max_chunk - 1); part = min(max_chunk - offset, iov_iter_count(iter)); @@ -212,8 +207,9 @@ ssize_t netfs_perform_write(struct kiocb *iocb, struct iov_iter *iter, finfo = netfs_folio_info(folio); group = netfs_folio_group(folio); - if (unlikely(group != netfs_group) && - group != NETFS_FOLIO_COPY_TO_CACHE) + if (unlikely(group) && + group != NETFS_FOLIO_COPY_TO_CACHE && + group != netfs_group) goto flush_content; if (folio_test_uptodate(folio)) { @@ -237,24 +233,22 @@ ssize_t netfs_perform_write(struct kiocb *iocb, struct iov_iter *iter, if (unlikely(copied == 0)) goto copy_failed; folio_zero_segment(folio, offset + copied, flen); - __netfs_set_group(folio, netfs_group); - folio_mark_uptodate(folio); - trace = netfs_modify_and_clear; - goto copied; + if (finfo) + trace = netfs_modify_and_clear_rm_finfo; + else + trace = netfs_modify_and_clear; + goto mark_uptodate; } /* See if we can write a whole folio in one go. */ if (!maybe_trouble && offset == 0 && part >= flen) { copied = copy_folio_from_iter_atomic(folio, offset, part, iter); if (likely(copied == part)) { - if (finfo) { + if (finfo) trace = netfs_whole_folio_modify_filled; - goto folio_now_filled; - } - __netfs_set_group(folio, netfs_group); - folio_mark_uptodate(folio); - trace = netfs_whole_folio_modify; - goto copied; + else + trace = netfs_whole_folio_modify; + goto mark_uptodate; } if (copied == 0) goto copy_failed; @@ -270,8 +264,10 @@ ssize_t netfs_perform_write(struct kiocb *iocb, struct iov_iter *iter, * accept the partial write. */ finfo->dirty_len += finfo->dirty_offset; - if (finfo->dirty_len == flen) - goto folio_now_filled; + if (finfo->dirty_len == flen) { + trace = netfs_whole_folio_modify_filled_efault; + goto mark_uptodate; + } if (copied > finfo->dirty_len) finfo->dirty_len = copied; finfo->dirty_offset = 0; @@ -303,6 +299,7 @@ ssize_t netfs_perform_write(struct kiocb *iocb, struct iov_iter *iter, goto copied; } + /* Do a streaming write on a folio that has nothing in it yet. */ if (!finfo) { ret = -EIO; if (WARN_ON(folio_get_private(folio))) @@ -311,10 +308,8 @@ ssize_t netfs_perform_write(struct kiocb *iocb, struct iov_iter *iter, if (unlikely(copied == 0)) goto copy_failed; if (offset == 0 && copied == flen) { - __netfs_set_group(folio, netfs_group); - folio_mark_uptodate(folio); trace = netfs_streaming_filled_page; - goto copied; + goto mark_uptodate; } finfo = kzalloc_obj(*finfo); @@ -343,7 +338,7 @@ ssize_t netfs_perform_write(struct kiocb *iocb, struct iov_iter *iter, finfo->dirty_len += copied; if (finfo->dirty_offset == 0 && finfo->dirty_len == flen) { trace = netfs_streaming_cont_filled_page; - goto folio_now_filled; + goto mark_uptodate; } trace = netfs_streaming_write_cont; goto copied; @@ -359,13 +354,33 @@ ssize_t netfs_perform_write(struct kiocb *iocb, struct iov_iter *iter, goto out; continue; - folio_now_filled: - if (finfo->netfs_group) - folio_change_private(folio, finfo->netfs_group); - else - folio_detach_private(folio); + /* Mark a folio as being up to data when we've filled it + * completely. If the folio has a group attached, then it must + * be the same group, otherwise we should have flushed it out + * above. We have to get rid of the netfs_folio struct if + * there was one. + */ + mark_uptodate: + priv = folio_get_private(folio); + if (likely(priv == netfs_group)) { + /* Already set correctly; no change required. */ + } else if (priv == NETFS_FOLIO_COPY_TO_CACHE) { + if (!netfs_group) + folio_detach_private(folio); + else + folio_change_private(folio, netfs_get_group(netfs_group)); + } else if (!priv) { + folio_attach_private(folio, netfs_get_group(netfs_group)); + } else { + WARN_ON_ONCE(!finfo); + if (netfs_group) + /* finfo->netfs_group has a ref */ + folio_change_private(folio, netfs_group); + else + folio_detach_private(folio); + kfree(finfo); + } folio_mark_uptodate(folio); - kfree(finfo); copied: trace_netfs_folio(folio, trace); flush_dcache_folio(folio); diff --git a/include/trace/events/netfs.h b/include/trace/events/netfs.h index 67f6d56c94ce..1f5e3a5af08a 100644 --- a/include/trace/events/netfs.h +++ b/include/trace/events/netfs.h @@ -179,7 +179,9 @@ EM(netfs_whole_folio_modify, "mod-whole-f") \ EM(netfs_whole_folio_modify_efault, "mod-whole-f!") \ EM(netfs_whole_folio_modify_filled, "mod-whole-f+") \ + EM(netfs_whole_folio_modify_filled_efault, "mod-whole-f+!") \ EM(netfs_modify_and_clear, "mod-n-clear") \ + EM(netfs_modify_and_clear_rm_finfo, "mod-n-clear+") \ EM(netfs_streaming_write, "mod-streamw") \ EM(netfs_streaming_write_cont, "mod-streamw+") \ EM(netfs_flush_content, "flush") \